Edible antimicrobial films are an innovation within the biodegradable active packaging concept. They have been developed in order to reduce and/or inhibit the growth of microorganisms on the surface of foods. This study developed an edible antimicrobial film based on yam starch (Dioscorea alata) and chitosan and investigated its antimicrobial efficiency on Salmonella enteritidis. A solution of yam starch (4%) and glycerol (2%) was gelatinized in a viscoamilograph and chitosan added at concentrations of 1%, 3% and 5%. Films with and without chitosan were produced by the cast method. To evaluate the antimicrobial activity of the films, two suspensions of S. enteritidis were used in BHI medium, corresponding to counts of 2 ¥ 10 8 and 1.1 ¥ 10 6 CFU/ml. The suspensions (50 ml) were poured into flasks. The films were cut into 5 ¥ 5 and 5 ¥ 10 cm rectangles to be used at ratios of 1 : 1 (1 cm 2 /ml microorganism suspension) and 2 : 1 (2 cm 2 /ml). The film 30 mm thick on average. As a control, pure chitosan at an amount corresponding to that contained in the 3% and 5% films (5 ¥ 10 cm) was added to flasks containing the microorganism suspension. Also, flasks containing only a suspension of S. enteritidis were used as control. The suspensions, in flasks, were kept at 37°C in a waterbath with agitation. Suspension aliquots were removed every hour for reading the optic density (OD 595 ) and plating onto PCA medium. The results showed that chitosan has a bactericidal effect upon S. enteritidis. Films treated with chitosan at different concentrations showed similar antimicrobial efficiency, in addition to being dependent on diffusion. The chitosan-treated films caused a reduction of one to two log cycles in the number of microorganisms, whereas the pure chitosan presented a reduction of four to six log cycles compared with the control and starch film. The films showed good flexibility.

a b s t r a c tEscherichia coli O:157:H7 adhesion and potential to form biofilm on three different surfaces commonly used in the food industry was evaluated using probabilistic models; the surfaces tested were stainless steel 304 (SS304), poly(vinyl chloride) film covered with thick cloth (PVC1) and poly(vinyl chloride) film covered with thin cloth (PVC2). Using a Central Composite Rotational Design (CCRD), the effect of contact time (0 h, 7 h, 24 h, 41 h and 48 h) and temperature (12 C, 17 C, 28 C, 39 C and 44 C) on the probability of achieving a particular adherent cell count (Log 10 CFU cm À2 ) was determined. By analyzing response surface plots and their corresponding contour plots and by determining quadratic equations for each surface, experimental values were shown to be significant in accordance with predicted values in all cases. The adjusted determination coefficient (R adj 2 ) was 90.5%, 97.2% and 98.9% for SS304, PVC1 and PVC2, respectively, and the level of significance was P 0.001. The bias factor (B f ) and accuracy factor (A f ) both approached 1.0 for the three surfaces evaluated. The model equations for predicting optimum response values were verified effectively by a validation data set for all surfaces evaluated. Therefore, an RSM provides a useful and accurate method for predicting E. coli O157:H7 adhesion and potential to form biofilm on SS304, PVC1 and PVC2 and could be considered to be a standard way to ensure food safety with respect to E. coli O157:H7 contamination through adhesion and biofilm formation.

Staphylococcus spp. can survive in biofilms for long periods of time, and they can be transferred from one point to another and cause environmental contamination in food processing. The aim of this study was to detect Staphylococcus strains isolated from a poultry processing plant by the presence of adhesion genes and the phenotypic production of exopolysaccharide. In the present study, the production of exopolysaccharide and the presence of adhesion genes in 65 strains of Staphylococcus spp. were evaluated. All strains of Staphylococcus spp. produced exopolysaccharide, as confirmed by formation of black and opaque colonies in Congo Red Agar. The variation of sucrose content was critical for the production of exopolysaccharide in Congo Red Agar since at low sucrose concentrations all strains presented a characteristic result, i.e., there was no exopolysaccharide production. The atl gene was found in all strains, and the icaA and icaD genes were found in 97% of them. The data obtained suggest that Staphylococcus spp. isolated from the poultry processing plant evaluated has a potential for biofilm formation. An efficient control of this microorganism in food processing environment is necessary as they may represent a potential risk to consumers.

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Vários tipos de alimentos são implicados em intoxicações gastrointestinais por Staphylococcus aureus, sendo frequentemente relacionado com carne e derivados, devido às propriedades de atividade de água, pH, nutrientes e a extensiva manipulação destes alimentos durante o processamento. Este trabalho teve por objetivo identificar cepas potencialmente toxigênicas de Staphylococcus isoladas de diferentes nichos em uma unidade de abate de frango de corte, bem como avaliar a resistência à diferentes antimicrobianos. De um total de 120 isolados, 75 foram considerados como típicos do gênero Staphylococcus, sendo 63,7% coagulase positiva e 37,3% coagulase negativa. Pela técnica de Reação em Cadeia de Polimerase (PCR) confirmou-se que 86,67% dos isolados eram pertencentes ao gênero Staphylococcus pela detecção do gene tuf e 77,33% da espécie S. aureus pela amplificação do gene nuc. Verificou-se a presença do gene sec em duas cepas, sendo uma delas estafilococos coagulase negativa. A maioria dos isolados foram resistentes à sulfonamida (98,5%), ácido nalidíxico (89,3%) e penicilina G (87,70%). Dentre os isolados resistentes à penicilina, 4,60% foram oxacilina resistentes e 1,5% vancomicina resistentes. Palavras-chave: Staphylococcus aureus, coagulase negativa, resistência à antibioticos, enterotoxinas